a(n) = (n+1)*(2*n+2)!/(n+2).A274136a(n) = (n+1)*(2*n+2)!/(n+2).Terms a(0) =1a(1) =16a(2) =540a(3) =32256a(4) =3024000a(5) =410572800a(6) =76281004800External referencesoeis: A274136